pngcmd="(./ps2png 512 512 /Users/jc/w/tmp/Tune-46659-Knot.ps) >>/Users/jc/w/tmp/Tune-46659-get.log 2>&1" returned status 256
http://roaringjelly.org/~jc/music/book/JohnWalsh/Knot.abc

Error exit status 256; here are some files to check:
[P=tuneget V=1/1 B=0 scale=0.70 512x512 PNG]
filesizedescription
Tune-46659-Knot.abc 2991 ABC music file with the extracted tune(s)
Tune-46659-Knot.ps 39555 PostScript
Tune-46659-Knot.txt 2991 Plain-text file with the extracted tune(s)
Tune-46659-get.log 4266 Log file, useful mostly for debugging
These files should be available for 24 hours.